The desirability of injecting materials into avian eggs during incubation has been recognized for some time. Initially, the purpose of injecting eggs was to prepare various vaccines using the egg as a growth medium for the vaccine. More recent developments have involved injecting live embryonated eggs for the purpose of accomplishing some beneficial or therapeutic effect on the embryo or the bird that eventually hatches from the egg. Such beneficial effects include increased growth, disease resistance due to in ovo vaccination, increased percentage hatch of multiple incubated eggs, and otherwise improved physical characteristics of hatched poultry.
Several basic techniques and injection devices for injecting materials into live embryonated eggs have been described, including forcing fluids through the egg shell using pressurization and physically forming an opening in the shell of an egg and then adding the desired material (e.g., injection using syringe and needle arrangements). One traditional method has been syringe injection of eggs by hand.
Several injection devices seal the injection hole after injection to prevent leakage and contamination. U.S. Pat. No. 4,593,646 to Miller et al. discloses a method and apparatus for automatic egg injection in which support plates hold and properly position a plurality of injection devices and eggs. Each egg is sealed after injection by heat coagulating the albumin located near the injection hole. An additional sealant is then applied to the outer shell by dipping each egg into a bath of the sealant. The '646 patent does not disclose sealing the egg prior to injection.
U.S. Pat. No. 4,040,388 to Miller discloses a method and apparatus for automatic egg injection in which the downwardly facing small end of an egg is punctured. The portion of the device which punctures the egg is heated in the '388 method, allegedly sterilizing the exterior of the egg (thus preventing infection during injection) and also sealing the hole by heat coagulating a small portion of the egg albumin. The '388 patent does not disclose sealing the egg prior to injection.
U.S. Pat. No. 2,477,752 to Kiss discloses a method of injecting fertile eggs for the purpose of producing chicks having down of predetermined colors. The '752 patent discloses injecting the egg manually with a syringe and thereafter by sealing the opening in the egg. While the patent states that care should be taken to prevent air from entering the egg, no method for preventing the entrance of air is provided. Sealing the egg prior to injection is not disclosed.
U.S. Pat. No. 5,136,979 to Paul et al. discloses an apparatus and method for injecting a plurality of eggs to the same depth and location even when the eggs are of varying sizes and are misaligned. The apparatus includes a means for sterilizing the egg punch and needle sections after each injection. U.S. Pat. No. 5,056,464 to Lewis discloses an apparatus and method for injecting a plurality of eggs in which a suction cup apparatus is used for grasping each egg. U.S. Pat. No. 4,903,635 to Hebrank discloses a high speed automated injection system in which eggs are lifted using suction devices and separate devices are used for forming an opening in the egg shell and for injecting a fluid substance.
Some egg injection devices deliver material through the small end of an egg into the albumin. Injecting material through the large end of an egg and into the air sac above the albumin is not appropriate for delivery of all materials. Delivery into the albumin, however, increases the risk of leakage of albumin and ingress of air and contaminants after injection. Methods of injecting material into the albumin of eggs on a rapid basis should preferably provide means for preventing air and contaminants from entering the albumin, and means for preventing leakage of albumin, after injection.